function loadJSON(sPath) { // Read, parse and return the a JSON file.
  // This only works from the background or options page because of cross-origin restrictions.
  var oXHR = new XMLHttpRequest();
  console.log('Load JSON: ' + sPath);
  oXHR.open("GET", chrome.extension.getURL(sPath), false);
  oXHR.send();
  var oOptionsStructure = JSON.parse(oXHR.responseText);
  return oOptionsStructure;
}